The present invention relates to a plasma addressed liquid crystal display, and more particularly to a plasma addressed liquid crystal display having a plasma address portion of an improved structure, thereby having an improved manufacturing.
There are several types of display devices such as a conventional cathode ray tube using a high speed electron beam, a vacuum fluorescent display using low speed electron beam, a plasma display using gas discharge, an electro-luminescence (the so-called E.L) display, a liquid crystal display using the electro-optic effect, etc. These display devices are different in function and structural characteristics, so that according to their characteristics, they have been selectively applied.
The common point of these display devices is in that an electrical picture signal or data signal, etc. is visualized. In various ways, the structures and functions are improved and developed.
Recently, a new matrix-type display which is constituted by the combination of a plasma discharge display, and an electro optic display, i.e. a liquid crystal display, is disclosed in U.S. Pat. No. 4,896,149 by Tektronix. This display in which one line is addressed by plasma discharge is structured in such a way that, as shown in FIG. 1, a liquid crystal shutter 10 where a plurality of stripe-like pixel electrodes 14 are arranged in parallel is lapped over a plasma addressing portion 20 where a plurality of unit discharge lines 21 are arranged perpendicular to the stripe-like pixel electrodes 11 of the liquid crystal shutter 10. An ordinary back light generator (not shown) is provided at the rear of plasma addressing portion 20.
In detail with reference to FIG. 2, first of all, in the liquid crystal shutter 10, a liquid crystal 16 is injected between two plates, i.e., transparent front plate 12 and middle plate 13, and a stripe-like pixel electrode 14 is formed on the inner surface of the front plate 12. In the plasma addressing portion 20, a plurality of grooves 24 for forming a discharge line 21 in perpendicular to the strip-like pixel electrodes 14 are formed in parallel on the rear plate 25, and a pair of electrodes 22 and 23 are provided on the both bottom sides of each groove 24. The rear plate 25 is closely adhered to the middle plate 13 of the liquid crystal shutter 10, so that the groove 24 forms a sealed discharge space, where a discharge gas is filled.
In liquid crystal shutter 10, since a data signal is applied to a selected pixel electrode 14, a potential for activating the liquid crystal is formed along a selected pixel electrode 14. In plasma addressing portion 20, according to the ionized state of each discharge line due to the plasma discharge of each sequentially-selected plasma scanning line 21, a positive potential for activating the liquid crystal 16 is formed linearly along scanning line 21 on middle substrate 13 in contact with the liquid crystal. Accordingly, a potential difference is formed by a selected pixel electrode 14 of liquid crystal shutter 10 and scanning line 21 of plasma addressing portion 20. Liquid crystal 16 positioned at the intersection is activated and oriented by the potential difference at the interconnection, which forms a light passing area through which light from the rear ward back light generator passes.
In other words, in plasma addressing portion 20, when voltage of a predetermined potential is applied to a pair of parallel electrodes 22 and 23 on a sequentially selected scanning line, linear direct-current-discharge occurs between parallel electrodes 22 and 23. Due to this, a linear ionization region is formed along scanning line 21 on the thinner middle substrate 13. When the linear ionization region is formed on middle substrate 13 by the linear discharge on scanning line 21 selected by the scanning signal a data signal is selectively applied to data electrode 14 of the upper liquid crystal shutter 10. When liquid crystal is then activated by the potential difference at the intersection of the selected data electrode 14 and the selected and discharged scanning line 21 and is locally re-arranged, back light passes, forming one picture point.
Such a display is a planar display of special type in which a liquid crystal is oriented by the pixel electrode and the discharge line, and has the following disadvantages. As described above, since the structure of the addressing portion is based on the grooves 25 formed on the rear plate and the extra material sealing it, for instance, the middle plate 13 of the above liquid crystal shutter, its manufacturing process is very complicated. Moreover, the thickness of the middle plate is about 50 .mu.m or less, so that there is a high probability of being broken during handling. Thus, the maximum size of the middle plate is limited.
Meanwhile, since the electrode for plasma discharge is formed on the bottom of the groove of the rear plate, its manufacturing is very difficult. Accordingly, the manufacturing process has difficulties in that this conventional liquid crystal display cannot be applied with the convenient electrode manufacturing method such as the general silk screen printing method.